1. Technical Field
This invention pertains to grease injectors useful in well servicing lubricators to seal around and lubricate flexible line passing through the lubricator into and out of an underwater well, when servicing the well using wireline techniques. The invention pertains particularly to a grease injector useful in servicing underwater wells, which includes a remotely operable hydraulically actuated stuffing box for sealing around the flexible line.
2. Background Information
Stuffing boxes having a resilient seal which is compressed into sealing engagement with flexible line by hydraulic actuation are well known. Stuffing boxes of this type are used on lubricators or grease injectors as the primary seal for sealing the flexible line to the lubricator or grease injector in the lubricator.
U.S. Pat. No. 3,762,725 to Taylor discloses a wireline stuffing box with a sheave in which pressurized fluid may be conducted from a remote source and applied to opposite sides of a piston to compress the seal longitudinally to seal. U.S. Pat. No. 4,386,783 to Davis covers a stuffing box and packing nut in which the packing may be compressed manually or hydraulically to seal around rods or wireline passing through the stuffing box. In this structure, packing is compressed by conducting pressurized fluid from a remote source to act on a piston. The Davis structure includes a plug seal through which the line passes and which is moved into place by flow to prevent well outflow in case of line breakage. Both the aforementioned patents are incorporated herein for reference.
An example of a grease injector head having a stuffing box in which the packing is compressed to seal hydraulically is shown on page 298 of "General Sales Catalog" (OEC 5338), a publication of Otis Engineering Corporation, P.O. Box 819052, Dallas, TX 75381.
When servicing underwater wells, it has been found the hydraulically actuated stuffing box of Taylor, the hydraulically actuated packing nut and stuffing box of Davis and the stuffing box on the Otis Grease Head cannot be used. When these stuffing boxes are lowered into deep water, the high hydrostatic pressure of control fluid in the control line acts to compress the resilient packing much more than just into sealing engagement with the flexible line. The packing is compressed so much the line is "seized" by high frictional forces between the packing and line and the line cannot be lowered into or pulled from the well through the lubricator.